Hi!
There are several ways to change volume.
First of all: you should use some realtime stuff. Low buffersize, which you
can configure in the ecasoundrc file.
Then you can use the following three ways:
1. Use a static linear envelop:
ecasound -c -i input -o output -ea:100 -klg:1,0,100,3,0,1,3,1,6,0.5
This will start at 0sec 100% volume (0,1), go to 3sec full volume (3,1) and
take 3sec to half-volume (6,0.5).
Probably not esactly what you'd like.
2. Use a midi-controller:
ecasound -c -i input -o output -ea:100 -km:1,0,100,1,1
This will use mididevice from ecasoundrc and channel 1 and controller 1 (the
modwheel) to change volume. With this you can turn volume from 0 to 100%.
You could probably use some virtual midi-controller (I think the GUI offers
a few) or a hardware device.
3. You can use some kind of compressor or volume-automation, for example:
ecasound -c -i input -o output -eli:1982,2,0.8,1,10,0
This will use ladspa-plugin with id: 1982 (vlevel) to automatically adapt
volume. It's a kind of look-ahead compressor. See their website for more info.
You can find vlevel and steve Harris' plugins listed at:
http://linux-sound.org
Table of contents / audio plugins.
About your server problem: I don't know.
Hope that helps.
Kindest regards
Julien